Int. J. Mol. Sci. 2014, 15(6), 11064-11081; doi:10.3390/ijms150611064
Article

Does Prop-2-ynylideneamine, HC≡CCH=NH, Exist in Space? A Theoretical and Computational Investigation

1,2,* email, 1,3email, 1email and 1,4email
Received: 25 March 2014; in revised form: 6 May 2014 / Accepted: 12 May 2014 / Published: 19 June 2014
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: MP2, DFT and CCSD methods with 6-311++G** and aug-cc-pvdz basis sets have been used to probe the structural changes and relative energies of E-prop-2-ynylideneamine (I), Z-prop-2-ynylideneamine (II), prop-1,2-diene-1-imine (III) and vinyl cyanide (IV). The energy near-equivalence and provenance of preference of isomers and tautomers were investigated by NBO calculations using HF and B3LYP methods with 6-311++G** and aug-cc-pvdz basis sets. All substrates have Cs symmetry. The optimized geometries were found to be mainly theoretical method dependent. All elected levels of theory have computed I/II total energy of isomerization (ΔE) of 1.707 to 3.707 kJ/mol in favour of II at 298.15 K. MP2 and CCSD methods have indicated clearly the preference of II over III; while the B3LYP functional predicted nearly similar total energies. All tested levels of theory yielded a global II/IV tautomerization total energy (ΔE) of 137.3–148.4 kJ/mol in support of IV at 298.15 K. The negative values of ΔS indicated that IV is favoured at low temperature. At high temperature, a reverse tautomerization becomes spontaneous and II is preferred. The existence of II in space was debated through the interpretation and analysis of the thermodynamic and kinetic studies of this tautomerization reaction and the presence of similar compounds in the Interstellar Medium (ISM).
Keywords: Z-prop-2-ynylideneamine; tautomerization; thermodynamic; Interstellar Medium; DFT; MP2; CCSD; NBO
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MDPI and ACS Style

Osman, O.I.; Elroby, S.A.; Aziz, S.G.; Hilal, R.H. Does Prop-2-ynylideneamine, HC≡CCH=NH, Exist in Space? A Theoretical and Computational Investigation. Int. J. Mol. Sci. 2014, 15, 11064-11081.

AMA Style

Osman OI, Elroby SA, Aziz SG, Hilal RH. Does Prop-2-ynylideneamine, HC≡CCH=NH, Exist in Space? A Theoretical and Computational Investigation. International Journal of Molecular Sciences. 2014; 15(6):11064-11081.

Chicago/Turabian Style

Osman, Osman I.; Elroby, Shaaban A.; Aziz, Saadullah G.; Hilal, Rifaat H. 2014. "Does Prop-2-ynylideneamine, HC≡CCH=NH, Exist in Space? A Theoretical and Computational Investigation." Int. J. Mol. Sci. 15, no. 6: 11064-11081.

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